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Measurements

Writing an Experiment Report

During the two years of the IB physics course you will perform a number of experiments. You must keep a record of ALL the experiments which you perform. For a few of the experiments you will be required to present a full, detailed report, which will be graded. The grades will form part of your final result (remember, a significant percentage of your final result will be based on your practical abilities). It is recommended that your reports should be set out as follows.

 Title Introduction Diagram Method Results Theory Conclusion
 1 Title (Aim) The title must state clearly the aim of the experiment. It must tell the reader what you are trying to prove or measure. For example, “Ohm’s Law” is not a suitable title for an experiment report, whereas, “Experiment to verify Ohm’s Law” is a suitable title. Similarly, “Relative Density” is not a suitable title but “Experiment to measure the Relative Density of some common substances” is a suitable title. 2 Introduction If the experiment is designed to verify a law, state the law in the introduction. The introduction can also include such ideas as why the results/conclusions of the experiment are important in every-day life, in industry etc. (it might even include a little historical background, but not too much). 3 Hypothesis Before starting your investigation you usually have some idea of what you expect the results will show. The hypothesis is basically a statement of what you are expecting. For example, if you are trying to show how two variables are related, state the expected relation and try to give and explanation of you choice. For example, when Newton was thinking about gravitation, he assumed that the strength of the force of gravity would become weaker as one moved further from the body causing the field. He suggested that the relation between force and distance might involve the inverse of the distance squared and to defend this choice he pointed out that the surface area of a sphere depends on the square of its radius. Various observations then confirmed this suggestion. 4 Diagram In most cases a labelled diagram is useful. Every electrical experiment report must include a circuit diagram. If diagrams are drawn by hand, use a sharp pencil and a ruler. (If you use a computer, learn how to make the best use of your drawing program.) 5 Method The method section should give enough detail to enable another experimenter to repeat the experiment to see if he/she agrees with your results/conclusions. The method should include a description of the apparatus used what measurements you made (if possible, in the order you made them) what precautions you took to ensure the best accuracy possible a mention of any unexpected difficulties (and how you overcame them) 6 Results You should record all the measurements made during the experiment along with some indication of the uncertainty of each measurement. Whenever possible, present the results in the form of a table. 7 Theory This section should include any information which might help the reader to understand how you used your measurements to reach the aim mentioned in the title. For example, in one experiment, designed to measure the relative density of a substance, the actual measurements made are two distances. The theory section of a report on such an experiment must include a clear explanation of how these two distances are related to the relative density of the substance being measured. 8 Conclusion/Evaluation Every experiment report must have a conclusion. If your aim was to verify a law, state whether you have verified the law or not. If the aim was to measure a particular quantity (e.g. relative density), give the final measured value of the quantity in the conclusion. In the case of an experiment designed to measure some well known physical constant you should attempt to explain any difference between your result and the accepted result. For example, if you find g=9.5ms-2, you should try to think of the most likely cause of this obvious error. If the experiment results were in some way unsatisfactory, try to suggest how the investigation might be improved in order to improve accuracy of measurements or range of data obtained. This evaluation section should include comments on the apparatus used and the method employed.
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